Myrcia summa ( McVaugh 1958: 89 ) M.F. Santos (2016b: 29)

Santos, Matheus F., Lucas, Eve & Sano, Paulo T., 2018, A taxonomic monograph of Myrcia sect. Sympodiomyrcia (Myrteae, Myrtaceae), Phytotaxa 380 (1), pp. 448-450 : 448-450

19. Myrcia summa ( McVaugh 1958: 89) M.F. Santos (2016b: 29) ( Figures 3A , 12 and 50 to 53)

≡ Marlierea summa McVaugh. Type:— VENEZUELA. Amazonas: Cerro Sipapo (Paráque), 26–28 January 1949 (fl.), Maguire 28644 (holotype MICH!, isotypes NY!, S!, US! VEN [image!])

= Marlierea summa var. superior McVaugh (1958: 91) . Type :— VENEZUELA. Ilu-Tepui , Gran Sabana, 14 March 1952 (fl.), Maguire 33405 (holotype MICH!, isotype NY!)

= Marlierea summa var. calva McVaugh (1969: 69) . Type:— VENEZUELA. Bolívar: Chimantá Massif, 5 February 1955 (fl.), Steyermark 493 (holotype MICH!, isotypes F!, NY [two sheets]!, S!, US!)

= Marlierea vicina McVaugh (1969: 70) . Type :— GUYANA. Upper Mazaruni River Basin. Mt. Ayanganna, 7 August 1960 (fl.), Tillett 45172 (holotype MICH!, isotypes COL [image!], F!, NY!, S!, US!, VEN [image!])

Shrub to tree 1–15 m high. Epidermal peeling absent in immature parts (rarely present); trichomes ferruginous, brown, light brown to white, 0.1–0.3 mm long. Twig when immature brownish or straw-like (when dry), flattened, sulcate, not keeled, tomentose, minutely tomentose, pubescent, puberulent or with scattered trichomes; mature twig greyish or brownish (when dry), cylindrical, cortex slightly cracked, glabrescent to glabrous; branching mainly sympodial (rarely monopodial), 2–6 branches per node, epidermal protrusion present at the nodes, internode 2.0– 10.5 cm long; cataphyll scale-like, 1 mm long, present in all internodes, early deciduous, free, ovate, externally pubescent; terminal node with central and lateral buds developed or lateral ones undeveloped, tomentose, pubescent or puberulent. Leaf discolorous, chartaceous or coriaceous, blade 2.4–17.0 × 0.5–8.0 cm, narrowly elliptic, elliptic, oblong, lanceolate to widely ovate or obovate, apex caudate or acuminate to rounded, base attenuate or narrowly cuneate to obtuse, margin plane to slightly revolute, secondary veins 2–7 mm apart, held at an angle of 50–90° relative to the midvein, one or two marginal veins, the first 1–2 mm and the second 1 mm from the margin, tertiary veins conspicuous to inconspicuous; adaxial surface tomentose, minutely tomentose, puberulent or with scattered trichomes to glabrous when immature, glabrescent to glabrous at maturity, midvein sulcate to flat in the first half and flat in the second half, secondary veins inconspicuous (sometimes raised), pellucid dots conspicuous to inconspicuous, less than 5 to more than 15 per mm 2; abaxial surface tomentose, minutely tomentose, pubescent, puberulent or with scattered trichomes when immature, tomentose, pubescent, puberulent or glabrescent to glabrous at maturity, midvein raised, secondary veins raised or inconspicuous, pellucid dots conspicuous to inconspicuous, less than 5 to more than 15 per mm 2; petiole 3–17 × 1–2 mm, canaliculate, tomentose, minutely tomentose, pubescent, puberulent or with scattered trichomes when immature, pubescent, puberulent or glabrescent to glabrous at maturity. Inflorescence 1.5–7.5 × 1.5–8.5 cm, pyramidal, axillar at the terminal node, terminal dichasia usually with three flowers, 1–50 flowers, rachis tomentose, minutely tomentose, pubescent, puberulent or with scattered trichomes, 1–12 branching at the base, first internode of central rachis 1–2 mm wide, cylindrical to flattened, distal internodes flattened, opposite branching (rarely subopposite), 2–4 branching per node, epidermal protrusion present at the nodes (usually absent in the apical branches). Bract 1–5 × 1 mm, deciduous, lanceolate or ovate, concave, apex acuminate or acute, base truncate, adaxial surface tomentose, pubescent, puberulent to glabrous, abaxial surface tomentose, pubescent, puberulent or with scattered trichomes. Pedicel 0–2 mm long, cylindrical, tomentose, pubescent or puberulent. Bracteole 1–2 × 0.5–1.0 mm, deciduous, lanceolate or ovate, concave, apex acuminate or acute, base truncate, adaxial surface tomentose, puberulent to glabrous, abaxial surface tomentose or puberulent. Floral bud 3–5 × 1–4 mm, turbinate. Hypanthium 0.8–2.0 mm extending above the summit of the ovary, not tearing at anthesis (sometimes with a small vertical rupture), externally tomentose, pubescent or puberulent, pellucid dots inconspicuous (usually covered by the indumentum), internally glabrous; calyx 3–5-merous, lobes 0.4–2.4 × 0.8–3.6 mm, distinct from the hypanthium, deciduous, depressed ovate, widely depressed ovate or deltate, concave, apex rounded (rarely acute or obtuse), base truncate, externally tomentose, pubescent, puberulent or with scattered trichomes to glabrous, internally tomentose, minutely tomentose, pubescent or puberulent; corolla 3–6-merous, petals reddish, light brown to white, 0.8–3.2 × 1.0– 3.2 mm, depressed ovate to widely ovate, depressed obovate or very widely obovate, concave, apex rounded, base truncate, externally pubescent, puberulent or with scattered trichomes to glabrous, internally puberulent or with scattered trichomes to glabrous; staminal ring 0.2–0.4 mm wide, glabrous (rarely with scattered trichomes), stamens 67–112, filament 2.2–4.0 mm long, white, glabrous, anther 0.24–0.32 × 0.16–0.48 mm, square, oblong or transversely oblong; ovary 0.8–1.2 × 0.8–1.8 mm, 2-locular, each locule with two ovules, style 4.0– 4.8 mm long, glabrous, stigma punctiform, papillose. Fruit green to yellowish when immature, vinaceous at maturity, 6–11 × 6–11 mm, depressed globose or globose, base rounded, glabrescent to glabrous, remnants of calyx lobes present or not; seeds 1–3.

Distribution and Habitat:— Myrcia summa occurs throughout the Guiana Highlands, including south and eastern Venezuela (e.g. Ayuan-Tepuí, Chimantá Massif, Cerro Sipapo, Ilu-Tepuí), western Guyana (e.g. Cuyuni-Mazaruni and Potaro-Siparuni regions) and northernmost Brazil (e.g. Pico da Neblina, Serra do Aracá) ( Figure 12 ). It is found usually above 1000 m elevation, but there are records down to 600 m of elevation. The species inhabits different vegetation types: carrasco, campo rupestre, high montane forest, margin of watercourses and rocky outcrops.

Phenology:— It flowers from January to March and in May, July, August, October and December; flowering is concentrated in January and February. Specimens with fruits were found from October to March and in May, June and August (mature fruits in August, October, December and February).

Conservation Status:— The species has a relatively wide distribution in the Guiana Highlands (Extent of Occurrence ca. 323,100 km 2), including records in many tepuis, which are protected areas; it is also found in more than 10 locations. However, the small Area of Occupancy (92 km 2) probably reflects its real distribution because the species occurs mainly in high elevation areas scattered through the region. This conflicting information led us to consider Myrcia summa as Data Deficient (DD; IUCN 2001).

Discussion:— Myrcia summa has morphological similarity with Myrcia mutabilis , sharing inconspicuous venation on the adaxial surface of leaf blade and sympodial branching. It differs from Myrcia mutabilis in the strongly ferruginous indumentum (versus ochraceous) and the narrower floral bud. Myrcia summa often shows a slight split in the hypanthium tissue at anthesis, probably because the floral bud is relatively narrow; other floral features are standard for Myrcia sect. Sympodiomyrcia .

The species has great morphological plasticity; this is reflected in the current synonymy: Marlierea summa var. calva , with big, glabrous leaves; Marlierea summa var. superior , with leaves with nearly rounded apices (which are usually caudate) and conspicuous and raised venation on both surfaces (rare in the species). Regarding the synonym Marlierea vicina , specimens from the type locality have an ochraceous indumentum, chartaceous leaves, thicker inflorescences, longer persistent bracts and bigger floral buds.

Available illustrations and images:— Holst et al. (2003; as Marlierea summa ).

Additional specimens examined:— BRAZIL. Amazonas : Mun. Barcelos, 28 January 1978 (fr), N.A.Rosa 2264 (MG!, MO!) ; ibidem, 1200–1400 m, 0 ° 51’0”N, 63 ° 21’0”W, 19 February 1984 (fr), G.T. Prance 29174 (K!, NY!) ; Serra do Aracá , 1150–1250 m, 0 ° 51’0”N, 63 ° 22’0”W, 13 February 1984 (fr), A.S.Tavares 19 (INPA!, NY!) ; ibidem, 1200 m, 0 ° 0’0”N, 63 ° 0’0”W, 13 February 1984 (fr), G.T. Prance 29040 (F!, INPA!, K!, MO!, NY!, RB!, UB!, US!) ; ibidem, 1150–1250 m, 0 ° 51’0”N, 63 ° 22’0”W, 15 February 1984 (fr), I.L. Amaral 1594 (INPA!, K!, MG!, NY!, US!) . GUYANA. Mount Wokomung , 1530 m, 5 ° 50’0”N, 59 ° 50’0”W, 14 July 1989 (fl), B.M. Boom 9232 (MO!, NY!) ; ibidem, 1650 m, 5 ° 50’0”N, 59 ° 50’0”W, 7 July 1989 (fl), B.M. Boom 9125 (MO!, NY!) . Cuyuni-Mazaruni, 902 m, 5 ° 37’3,6”N, 60 ° 13’8,3”W, 4 December 2002 (fr), K.M. Redden 1398 (K!, US!) ; ibidem, 1500–2000 m, 5 ° 17’N, 60 ° 44’W, 24 February 1989 (fr), W. Hahn 5449 (K!, US!) . Mt. Roraima , 22 October 1973 (fl), R. Persaud 91 (K!). Pakaraima Mountains, 787 m, 5 ° 35’23,7”N, 60 ° 13’1, 9”W, 31 January 2004 (fr), K.M. Redden 1638 ( US!) ; ibidem, 1550–1650 m, 5 ° 4’N, 59 ° 52’W, 19 November 1993 (fr), T.W. Henkel 4508 ( US!) ; ibidem, 1530 m, 5 ° 4’N, 59 ° 62’W, 20 February 1993 (fr), T.W. Henkel 1519 (B!, US!) . VENEZUELA. Amazonas: Cerro de la Neblina, 1700–1800 m, 10 January 1954 (fl), B.Maguire 37223 (MICH!, NY!) ; ibidem, 1600–1800 m, 22 November 1958 (fr), B. Maguire 42175 (MICH!, NY!) . Cerro Sipapo , 1500 m, 10 January 1949 (fl), B.Maguire 28262 (MICH!, NY!) ; ibidem, 1500 m, 10 January 1949 (fl), B. Maguire 28270 (F!, K!, MICH!, NY!) ; ibidem, 1400 m, 15 December 1948 (fl), B. Maguire 27688 (MICH!, NY!) ; ibidem, 1400 m, 25 December 1984 (fl), B. Maguire 27906 (MICH!, NY!, W!); ibidem, 600 m, 2 February 1949 (fr), B. Maguire 28719 (MICH!, NY!) . Dept. Atabapo , 1500–1600 m, 3 ° 35’N, 65 ° 23’W, 11 March 1985 (fl), R.L.Liesner 18555 ( MO!) . Dept. Rio Negro , Cerro Aracamuni, 1550 m, 1 ° 26’N, 65 ° 47’W, 16 October 1987 (fl), R.L.Liesner 22002 (BM!, F!, MO!) ; Cerro Aracamuni , 1400 m, 1 ° 32’N, 65 ° 49’W, 25 October 1987 (fl, fr), R.L.Liesner 22419 ( MO!) ; Cerro de la Neblina , 1750–1850 m, 0 ° 54’N, 66 ° 4’W, 16–18 February 1984 (fl), R.L.Liesner 16101 (K!, MO!) ; ibidem, 1900 m, 16– 17 October 1970 (fr), J.A. Steyermark 103972 (MICH!, US!) ; Cerro Sipapo , 1600 m, 8 January 1949 (fl), B.Maguire 28257 (G!, MICH!, NY!, RB!) ; Cerro Sipapo , 1600 m, 8 January 1949 (fl), B.Maguire 28237 (F!, G!, K!, MICH!, NY!, RB!, S!, US!) . Rio Cuao ( Rio Orinoco ), 125 m, 3 January 1949 (fr), B. Maguire 28172 (NY!, S!). Bolívar: Ayan-Tepui, 1800 m, 5 ° 56’0”N, 62 ° 34’0”W, 28 August 1983 (fr), G.T. Prance 28281 ( NY!) . Cerro Guaiquinima , 1200 m, 2 January 1952 (st), B.Maguire 33018 ( NY!) ; ibidem, 1680 m, 5 ° 38’N, 63 ° 45’W, 30 May 1978 (fr), J.A. Steyermark 117527 ( MICH!) . Cerro Jáua , 1922–2100 m, 4 ° 45’N, 64 ° 26’W, 22–27 May 1967 (fl), J.A.Steyermark 97856 (F!, MICH!, MO!) ; ibidem, 2000 m, 4 ° 48’50”N, 64 ° 34’10”W, 27 February 1974 (fl), J.A. Steyermark 109632 (F!, K!, MICH!) . Chimantá Massif , 1880–1995 m, 26 February 1955 (fl), J.A.Steyermark 1134 (F!, MICH!, NY!, RB!) ; ibidem, 22000– 2300 m, 20 June 1953 (fr), J.A. Steyermark 75842 (F!, MICH!) ; Chimantá Massif (Sarvén-tepuí), 1450 m, 10 January 1953 (fl), J.J.Wurdack 34072 (G!, IAN!, K!, LE!, M!, MICH!, NY!, W!) . Distrito Piar , 2000 m, 5 ° 18’N, 62 ° 9’W, 26–29 January 1983 (st), J.A.Steyermark 128001 (F!, MO!, US!) . Ilu-Tepui , 1850–1900 m, 11 March 1952 (fl), B.Maguire 33378 (MICH!, NY!) . Mun. El Dorado , 800–1200 m, 6 March 1962 (fr), J.A.Steyermark 44 (MICH!, NY!) . Río Cuyuní , 1300–1380 m, 23–24 December 1970 (fr), J.A. Steyermark 104362 ( MICH!) . Total : 40 specimens .

Figures

FIGURE 3. A. Detail of the leaf of Myrcia summa showing foveolate dots (Prance 29040 [RB]). B. Wax peeling (white) on the leaf of Myrcia rupestris (Santos 641 [SPF]). C. Wax peeling (white) on the leaf of Myrcia costeira (Santos 851 [SPF]). D. Keeled twig of Myrcia costeira (Santos 851 [SPF]). E. Keeled twig of Myrcia densa (Santos 643 [SPF]). F. Leafy cataphyll of Myrcia subcordata covering immature leaves (Rochelle 55 [SPF]). G. Leafy cataphyll (indicated) of Myrcia costeira (Santos 851 [SPF]). H. Scale-like cataphyll (indicated) of Myrcia subavenia (Santos 715 [SPF]). Scales:A=4 mm; B–H=1 cm.

FIGURE 12. Distribution of Myrcia attenuata (triangles), Myrcia foveolata (squares) and Myrcia summa (circles). Continuous lines represent South American country and Brazilian state boundaries. The grey gradient represents elevation.

FIGURE 50. Images of representative specimens of Myrcia sect. Sympodiomyrcia species: Myrcia summa (holotype of Marlierea summa var. summa: Maguire 28644 [MICH]).